Oxidative stress in cancer cells generates oxygen free radicals which degrade cell membranes by lipid peroxidation. Polyunsaturated fatty acids are converted to alkanes that are excreted in the breath or degraded by cytochrome p450 enzymes. In a pilot study, an advanced new test for breath alkanes distinguished women with breast cancer from cancer-free controls. Hypothesis: The breath alkane test may provide a new biomarker of breast cancer. Experimental plan to test the hypothesis: Breath alkane tests will be performed in 170 women undergoing biopsy of a breast mass. The short-term aim of the research is to determine the sensitivity and specificity of the breath alkane test as a biomarker to breast cancer. Long-term aims of the research: If the breath alkane test is confirmed as a sensitive and specific biomarker of breast cancer, the instrumentation will be developed into a portable purpose-built apparatus. This device would be comparatively inexpensive and suitable for rapid mass screening of large populations of women for breast cancer. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE